Javascript timed array iteration

Sometimes you need to iterate on an array with a time delay between each iteration. For example, you have a list of UI elements. And you want to perform animation or process each components in a way to make it visible to user. If you dont use any delay there will be no UI feedback. User will think everything happened at once. Its better to provide an UI feedback on the work in progress.

Timed array iteration means you use a delay on each iteration. JavaScript has no sleep method. So its not possible to add delay like other languages. I used `window.setTimeout ` to achieve this. This is only available on browser based JavaScript. In server side JavaScript like nodejs, v8, rhino its not available. Here is the function.

function arrayWalkTimed(arr, dur, func){
    var p = arr[0]? arr[0]: null;
    if(p){
        func(p);
        window.setTimeout(function(){
            timed_array_walk(arr.slice(1), dur, func);
        }, dur);
    }
}

Parse Query String by pure JavaScrirpt

Here is a snipped I wrote today to parse Query String by pure JavaScript. Some people uses different JavaScript libraries. But from my older days when I used to parse GET parameter by perl I had a habit of writing this algorithm. I just translated it to JavaScript.

Here goes the code.

function getUrlParts(url){
// url contains your data.
var qs = url.indexOf("?");
    if(qs==-1) return [];
    var fr = url.indexOf("#");
    var q="";
    q = (fr==-1)? url.substr(qs+1) : url.substr(qs+1, fr-qs-1);
var parts=q.split("&");
var vars={};
for(var i=0;i<parts.length; i++){
var p = parts[i].split("=");
        if(p[1]){
vars[decodeURIComponent(p[0])] = decodeURIComponent(p[1]);
        }else{
            vars[decodeURIComponent(p[0])] = "";
        }
}
// vars contain all the variables in an array.
return vars;
}

Create Next Previous Javascript Bookmarklet for Slideshow Tutorial Ebook sites

Recently I was browsing http://talks.php.net. There were bunch of slideshows about php. I work on PHP most times. So It was good for me.
The problem arise when I saw some slide shows didn’t rendered correctly in html. so there was no next, previous button. I had to change the urls to navigate next, previous pages.
Most urls were in the format http://domain.com/path/slideshow/1, where 1 is the page number. Changing it to 2 led me to the 2nd page of the sildeshow.
I wanted it to make automated. Via javascript obviously ( being a big fan of JS).

So I made two Javascript bookmarklet button. So when you click the Next button, it will go to next page. And same for Prev button.
Following are the buttons. All you have to do is just drag those button to your Browsers Bookmark bar. Thats it!

Next Page

Prev Page

Note: Not all the urls will work. See below to get more idea.

  1. http://domain.com/path/slideshow/1 Will work
  2. http://domain.com/path/slideshow/1.html Will not work
  3. http://domain.com/path/slideshow/1.php. Will not work
  4. http://domain.com/path/slideshow-1. Will work
  5. http://domain.com/path/slide-2/show Will not work
  6. http://domain.com/path/slide-2/show.php Will not work
  7. http://domain.com/path/slide-2 Will not work
  8. http://domain.com/path/slideshow#1 Will work ! !

Sometimes those buttons discussed above may not work, eg, Manual, ebook etc sites. In that case use the following two buttons.
These are quite handy if you are browsing a site where next page cannot be guessed from url.

Next URL

Prev URL

Here is the code

Next Button:

var e=document.getElementsByTagName("link");
var g="getAttribute";
var l=window.location.href;
for(i=0;i<e.length;i++){
    r=e[i][g]("rel").toLowerCase();
    h=e[i][g]("href");
    if(r=="next"){
    l=h;
    break;
    }
}

Previous Button:

var e=document.getElementsByTagName("link");
var g="getAttribute";
var l=window.location.href;
for(i=0;i<e.length;i++){
    r=e[i][g]("rel").toLowerCase();
    h=e[i][g]("href");
    if(r=="prev"){
    l=h;
    break;
    }
}